Paul Rokosz took over the ailing American Express AXP Strategy Aggressive Fund/A (ISAAX) last June with a mandate to make it a star performer.

For the 38-year-old Rokosz, it’s his first shot as the solo manager of a retail fund. He had co-managed another American Express offering, AXP Equity Select Fund/A (INVPX), for two years with Duncan Evered.

And he had been running institutional money with Evered and Gordon Fines, who has managed AXP New Dimensions Fund/A (INNDX) for 12 years.

Rokosz inherited a fund concentrated in telecom and tech.

“That is where change was needed most,” said Rokosz. “There were better opportunities for growth in other areas.”

And the concentration in sectors made the fund too volatile.

One part of running a fund, Rokosz allows, is stock selection. But another key part is risk management.

“The question is how do you build a successful portfolio and trade off risk and reward,” Rokosz said.

In Rokosz’s case, he cut the number of names from more than 140 to under 90, sold off tech and telecom and spread money among more industry groups. Much of the money went into health care.

“We’ve always been able to find opportunities in health care,” he said.

One choice was Manpower Inc (MAN). From a multiyear high of 43.30 a year ago, the global temporary worker firm is trading at about 33. Rokosz still thinks the company will be a winner. It has accelerating sales and earnings the past three quarters.

Rokosz shares the growth-investing philosophy of Fines, who hunts for stocks with above-average sales and earnings growth, and rising profit margins for his large-cap American Express New Dimensions. American Express just opened an office in San Diego, headed by Fines.

Evered and Rokosz moved from the firm’s Minneapolis headquarters to join Fines, who has been there four years.

The managers also believe in pruning the portfolio of losers and letting the winners run.

Fines and the other managers in San Diego keep a close watch on a stock’s performance relative to the S&P 500 the past three, six and 12 months. If a stock lags in all three periods, it goes on the “wounded duck list.” They take a close look at the reasons they still hold it.

Maybe new management or a hot product in the pipeline might bolster arguments for hanging on to it. Or the managers think they understand the company’s prospects better than other investors. Otherwise, it’s time to sell.

Also, to control risk, the managers will trim a holding to keep it from exceeding 5% of the portfolio.

Rokosz says he runs the fund with a strategy similar to AXP Equity Select, which he previously co-managed. But for Strategy Aggressive he sets aside 20% of assets for more aggressive plays.